Magnetic chuck



Aug. 21,l 1934. 'F.L. slMMoNs UAG'NETIG CHUCK 'Filed Nov. 17.j1'952 Sheets-Sheet 2 nfl,

- JNvENTR- dm. ,Jim maar l BY F. L. SIMMONS ulusma'rlc caucx Filed NOV'. 17, 1932 Vil v |NYENTOR- jpranlqfzmmom BY l i /Ww ZA r M TTORNEYS Aug. 2l, 1934.

Patented Aug. 2l, 1934 MAGNETIC CHUCK Frank L. Simmons, Woonsocket, R. I.,.assignor to The Taft-Peirce M anufacturing Company,

Woonsocket, R. I., a corporation of Rhode Island Application November 17, 1932, Serial No. 643,044 5 claims. (o1. F15-.367)

The present invention comprises a novel magnetic chuck.

It has been the practice of the art heretofore in the manufacture of magnetic chucks. to cast the chuck body, which is a shell enclosing the electrical units, and to mount in the shell a cast core member having core pole pieces upstanding from an integral base to receive the energizing coils. Then, a cast face plate was made up to form a grid like member in which face plate pole pieces were set by use of non-magnetic material of the type of Babbit metal. Magnetic chucks lare usually built for specific purposes. Some of them are circular in form to be used on rotating parts like a rotating grinder head, and others are rectangular in form to be used on the machines of the planer 'or milling type. In each case, specic chucks are usually designed for the particular use to which the chuck is intended. The result of this is that magnetic chucks heretofore have been expensiveto manufacture in that separate patterns were required for each particular job. Furthermore, castings had to be made from these patterns and then a very large amount of hand or machine work was required to place the castings in condition for'assembly as a'chuck. This meant that several weeks would intervene between the time when the chuck was ordered and the time it could be completed. The castings, particularly for the core pole pieces, almost always had rough corners which, unless they were carefully hand worked, would puncture the thin insulation of the coils when thelcoils were forced over the core pole pieces. Furthermore, the castings at the bottom of the upstanding core pole pieces Where they joined the core base plate usually presented a rounded corner which had to be worked out in order to permit the coil to set solidly on the pole piece.

Magnetic chucks are frequently used for wet grinding and it is essential that the liquids be kept away from the electric circuits. Chucks made of cast iron, as has been the universal practice, were frequently so porous as to permit the entry of the grinding fluids to the interior of the chuck and in this way, increased the liabilities of short circuits. It was very diflicult to locate small blow holes, and also diflicultto seal these small holes when they were located. Cast iron, partly due to porosity and partly due to its non-magnetic content, does not possess the same efhciency for the transmission of magnetic lines of force that is attained by the use of ,worked or wrought metal. Therefore, cast iron chucks are liable to heat, consequently, diverting a part of the electrical energy into non-useful work,

namely, the heating of the chuck instead of magnetizing the metal of the chuck.

The present invention comprises a chuck with the majority of the elements formed of wrought metal and this is accomplished by assembling the several elements of the chuck as individual pieces homogeneously united together, as by welding.

The present invention also contemplates cutting the various lpieces required in the present construction from plates or bars of wrought metal, and then assembling the parts in the manner specified. A chuck constructed in this manner possesses important advantages over prior vart structures and is very much more flexible in manufacture, in that the use of patterns and castings is completely eliminated, and a chuck may be manufactured in a very short time from ordinary stock plates or flat bars of wrought yiron or mild steel.

The present invention also has a great advantage in that the various operations, such as drilling and shaping the parts, can be done on`v individual pieces before being permanently Welded or fastened together and this further facililtates the manufacture of the chuck. Furthermore, a chuck in accordance with the present invention has a wide latitude of designs without substantially increasing the cost in production. Under the old practice, it was necessary to make separate patterns and castings for each design.

By producing a chuck in this manner, the bottom of the cores of the pole pieces may extend through the base plate and come directly into contact with the bed of the machine, thereby increasing the magnetic characteristics of the chuck by forming a larger path for the lines of magnetic force.

, Because of the increased eiciency resulting from the construction of the present chuck, the weight of the chuck may be diminished and also the height of the chuck may be lessened. This is important in connection with machine tools wherein the space between the bed of the machine and the operating tool is limited..

The construction of the chuck also permits the assembly operations, preferably welding, to be done at the most convenient place for such operations. For example, the core pole structure may be welded on the bottom where there is ample room for the welding operations -and this results in a structure in which clear square shoulders are provided in the seats of the coils. y The welding, either by torch or by electric arc using a mild steel welding rod, unites the parts with homogeneous metal and forms a shell of non-porous solid metal impervious to liquids and of greatly improved magnetic qualities.

The present invention comprises a very substantial advance in the art as has been fully demonstrated by commercial chucks having the construction and arrangement of parts in accordance with the present disclosure.

It is realized that the present invention may be practiced by departing from the specic disclosure herewith without departing from the spirit of the invention. Therefore, the disclosure 5 herewith is to be understood as illustrative and the chuck tion of a face plate shown in Fig. 5.

Fig. 7 is a longitudinal sectional view through a completed face plate and showing the upper ends of the core pole pieces.

Fig. 8 is an enlarged sectional view of a portion of a longitudinal section of the face plate shown in Fig. 7.

Fig. 9 is a perspective view showing a face plate pole piece.

Fig. 10 is an enlarged View of a longitudinal section of a face plate before vthe pole pieces are set therein.

Fig. 11 is a plan view of the shell of a chuck showing the parts separated before assembly.

Fig. 12 illustrates steps in the manufacture and assembly of the core pole pieces and base plate.

Fig. 13 illustrates a step in the manufacture of the face plate.

According to the present invention, the elements comprising the present chuck are formed of wrought metal having desirable magnetic characteristics and one material which may be utilized is wrought mild steel or wrought iron. In accordance with the present invention, the bottom or base member 1 of the chuck comprises a section from a bar or plate of wrought magnetizable metal cut to the required length and having the required width. Openings 2 are cut in this plate of substantially the size and cross section of the core pieces 4. The cutting may be performed by the use of a cutting torch 5 as shown in Fig. 12 or otherwise as may be convenient. The core pole pieces 4 are sections cut from plates or bars having rounded edges and these core pole pieces 4 are forced through the openings 2 in such manner as to make a drive t, so that the sides of theopenings 2 in the base plate are in intimate contact with the sides of the bottoms of the core pole pieces. These core pole pieces are forced through the openings 2 to such a distance as to protrude through the bottom of the base plate 1.

Side plates 6 and 7 are cut from bars or plates of suitable material to the correct height and length of the chuck. End plates 8 and 9 are also cut the required length from suitable stock having a width equal to the side plates 6 and 7. End pads or clamp bars 10 and 11 are cut from suitable bars of the proper size to lengths equal to the overall width of the chuck. The several parts are arranged as shown in Fig. 11 and are then clamped tightly together and homogeneously united as by welding. The ends of the core pole pieces are welded at 12 entirely around the lower ends of the core 'pole pieces. This weld securely locks the core pole pieces in place, and the weld is made at a convenient point for welding. The side and end plates are welded to the base member along the side joint at 14 and at the ends at l5 and 16. Each end is welded by outside seams 17 and 18 to the side Walls 6 and 7. The clamp bars 10 and 11 are welded to the top and bottom Welds 19 and 20. The end plates are also welded at 21 and 22 at their tops to the side plates 6 and 7. In this manner, the body of the chuck is built up and it will be observed that there' are no interior welds so that all interior corners are square as shown in Fig. 2. This is of great importance, particularly in setting the coils 24 down over the core pieces 4 in that the coil sets solidly on the base plate 1 and there is no roughness or protuberance on the sides of the core member which may tend to destroy the insulation on the coils. In this Way, the coils may be 4formed with very light in sulation and thereby increase the effectiveness of the coil on the core pole pieces and decrease the space required for the coils since compactness is important. Furthermore, the setting of the coil down solidly on the square shoulder adjacent the base member obviates any possibility of a fillet at the bottom of the core pole piece tending to wedge the coil spirals together and causing short circuits, as is a common difiiculty with cast core pole pieces. Furthermore, in casting core pole pieces, it is necessary to provide a slight taper to these core pole pieces to provide the drag necessary to pull the pattern from the sand. This wedge shape to the cast core pole piece members either required machining of the pole pieces or it required spacing the coil from the upper portion of the pole piece a sufficient amount to permit a non-tapered core to be placed over the core pole pieces. This caused air gaps that decreased the efiiciency of the chuck. In the present construction, the coils are in close proximity to the core pole pieces throughout their entire length in view of the fact that all opposed surfaces on the core pole pieces are parallel to the axes of the core pole pieces.

The face plate 23 for the chuck is cut from a suitable width piece of wrought metal in the form of a rectangular plate. Pole piece openings 25 are then cut in the face plate, and this op eration may also be performed with the cutting torch 5 as illustrated in Fig. 13. Preferably, after the face plate openings are cut, the side Walls 26 of these openings are roughened by a torch, or otherwise as illustrated in Fig. 13.

In order to provide a suitable depth to the face plate to carry face plate pole pieces, side bars 28 and 29 are Welded to the face plate along both edges as illustrated in Figs. 5 and 6 at 30 and 31, and end bars 32 and 34 are welded on both edges at 35 and 36 to the face plate and at their ends at 37 and 38 to the side bars 28 and 29. This results in the under part of the face plate, as shown in Figs. 5 and 6, comprising a low walled structure with face plate openings therein. It is to be understood that Fig. 5 illustrates the under portion of the face plate. Suitable screw holes 39 are provided through the face plate 23, in the side bars 28 and 29 and in the end bars 32 and 33 in order to permit assembly of the face plate on the finished shell of the chuck when the face plate is completed.

The face plate pole pieces 40 which contact with the upper ends of the core pole pieces 4 are preferably assembled from sections cut from three bars 41, 42 and 44. The sides of the bars 41 and 42 are preferably provided with beads 45 which may be formed by welding material to the sides of these bars, or the sides may be roughened in any suitable manner. The lower edges of the bars 41 and 42 are preferably chamfered at 46 and 47. The pole piece bars 4l and 42 are welded to the bar 44 by means of welds 48 on the bottom of the pole piece member and welds 49 on the interior of the pole-piece mem'- ber. These face plate pole pieces 40 are set in the openings in the face plate 23 and the spaces between the face plate pole pieces and the face plate is filled with soft metal 50 which preferably is of the nature of Babbit metal specially alloyed to form a non-magnetic metal alloy which tends to expand slightly on cooling in order to insure tight joints between the pole piece members. The purpose of roughening the face plate openings at 26, and the beads 45 or roughening on the pole pieces 40, is to provide interlocking surfaces which when embedded in the soft metal 50, securely anchor the face plate pole pieces 40 into the face plate 23.

After the parts have been fabricated as above specified and the coils 24 positioned over the core pieces 4 and suitably electrically connected with the conductors 51, which pass through an opening 52 in the side Wall of the chuck, a thin sheet of tin 54 is preferably placed over the core pole pieces and the assembled face plate is locked in position with machine screws 55. This sheet of tin 54 seals the coils against any liquid that might leak through the joints in the face plate. The entire chuck is nowassembled and ready for connection with suitable electrical switches to -complete the fabrication of the chuck.

While mild steel or wrought iron is the preferred materials from which, the magnetizable portions of the chuck is constructed, it is to be understood that various other wrought metals having desirable magnetic characteristics may be used and that various methods of welding the parts together to form a homogeneous structure may be practiced. The preferred method, however, is the use of arc welding with a wire or rod melted into the joints between the parts to be assembled to form a homogeneous connection of magnetizable metal. It is. desirable that the welded parts shall be forced into intimate contact with each other before the welding operation in order to facilitate the ow of magnetic lines of force through elements of the chuck. By permitting the core pole pieces to extend through the bottom plate to a plane determined by the side walls of the chuck, these core pieces may be individually brought into direct contact with the bed of a machine tool so that the bed of the machine tool, which is usually iron, augments the' passage of magnetic lines of force through the elements of the chuck. The complete circuit of the magnetic lines of force includes the core pole pieces, the bottom plate, the side walls of the chuck, the face plate, and the face plate pole pieces, and where the chuck is set directly on the bed ofthe machine, this bed also is a shunt passageway for magnetic lines of force from. the pole pieces to the bottom of the side walls. Y

By the use of wrought metal, a better finish may be provided for the chuck, which finish has a less tendency to rust than where cast metal is used as has been the practice heretoforeYV in the art. Furthermore, wrought metal such as plates or flat bars usually has a grain of metal extending lengthwise of the piece. -This grain in the core pole pieces, in the bottom plate, side and end walls of the shell, and in the face plate, extends in the direction of large fields of magnetic lines molecular bond between the several elements of the chuck.

What I claim is:

1. A magnetic chuck comprising pole pieceshaving the grain of the metal extend lengthwise of the pole pieces and a bottom plate, said bottom plate being formed with openings through which said pole pieces extend beyond the bottom of the bottom plate and with homogeneous metal uniting said pole pieces and said bottom plate.

2. A magnetic chuck comprising individual core pole pieces, a base plate provided with openings through which said core pole pieces extend, side members and end members secured to said base plate by homogeneous magnetizable metal, said sides and said ends of the core pole pieces extending below said base plate and terminating in a common plane whereby said side plates and said ends of the pole pieces may rest upon the bed of a machine tool, a wrought metal face plate mounted upon said side members and end members over said core pole pieces, said face plate being provided with openings, wrought metal face plate pole pieces extending' through said openings in the face plate, and non-magnetzable material between said face plate pole pieces and said face plate.

3. The method vof making electro-magnetic chucks comprising cutting openings by a hot gas flame in a plate of magnetizable metal to form a base plate, forcing fiat sections of magnetizable metal of substantially uniform length into said` openings to form pole pieces, and welding the pole pieces in place to comprise a base and pole piece section. cutting side pieces from plate of magnetizable metal of substantially uniform width, and welding said side pieces together and to said base and pole piece section.

4. The method ofy forming a face plate for electro-magnetic chucks comprising cutting pole piece openings in a at piece of magnetizable metal,y welding flat pieces of magnetizable metal' together to form a trough, inserting the sides of said trough through the openings in the face 1 plate and out4 of contact with the face plate, and

filling the spaces between-said face plate and l said trough with non-magnetizable 'material whereby the edges of the trough may comprise one magnetic pole-and the plate itself the other magnetic pole of the face plate.

5. The method of making electro-magnetic' lchucks comprising cutting openings in a plate Ofmagnetizable metal to form a base plate, inserting plates of magnetizable metal of uniform length of said openings, welding said plates in place, Welding plates of uniform width to said base plate to form the sides of the chuck, cutting openings through a plate of magnetizable metal to form a face plate, welding plates of magnetizable metal to form face plate pole pieces, extending the face plate pole pieces through the openings in the face plate and out of contact therewith, filling the spaces between the face plate pole pieces and the face plate with non-magnetizable material, fixing coilsv upon the pole pieces, and securing the face plate upon the sides of the chuck.

FRANK L. SIMMONS. 

